In recent years, soft silicone hydrogel contact lenses become more and more popular because of their high oxygen permeability and comfort. However, a silicone hydrogel material typically has a surface or at least some areas of its surface which is hydrophobic (non-wettable). Hydrophobic surface or surface areas will up take lipids or proteins from the ocular environment and may adhere to the eye. Thus, a silicone hydrogel contact lens will generally require a surface modification. A variety of surface modification approaches have been proposed to render silicone hydrogel contact lenses wettable. One of the approaches is to attach hydrophilic polymers onto contact lenses according to various mechanisms.
For example, U.S. Pat. No. 6,099,122, U.S. Pat. No. 6,436,481, U.S. Pat. No. 6,447,920, U.S. Pat. No. 6,465,056, U.S. Pat. No. 6,521,352, U.S. Pat. No. 6,586,038, U.S. Pat. No. 6,623,747, U.S. Pat. No. 6,730,366, U.S. Pat. No. 6,734,321, U.S. Pat. No. 6,835,410, and U.S. Pat. No. 6,923,978 disclose various methods for grafting a hydrophilic coating onto a contact lens having surface functional groups for photo- or chemical-grafting of hydrophilic polymers, in which the surface functional groups of the contact lens are either inherently present in the lens and derived from a monomer having a functional group or introduced by plasma treatment, plasma-induced graft polymerization, use of a functional photoinitiator, covalently attaching a photoinitiator and photografting of monomers with functional groups, or combinations thereof.
U.S. Pat. No. 6,623,786 discloses a method of photografting a hydrophilic polymer by dipping sequentially in a photoinitiator solution and a hydrophilic macromer solution and then by photocrosslinking the macromer.
U.S. Pat. No. 6,440,571 discloses a method for modifying the surface of a medical device (including a contact lens) to increase its biocompability or hydrophilicity by coating the device with a hydrophilic polymer by means of reaction between reactive functionalities of the hydrophilic polymer and reactive functionalities inherently presented on or near surface of the medical device (i.e., those functionalities derived from a vinylic monomer having a functional group in a lens formulation for making contact lenses.
However, those grafting methods have not been used in the commercial products due to their applicability limited to certain types of silicone hydrogel contact lenses having functional groups inherently presented in the lenses, their complexity, inadequate cost-efficiency, and/or inadequate time-efficiency. Therefore, there is still a need for a method of producing silicone hydrogel contact lenses with wettable and durable coating (surface) in a cost-effective and time-efficient manner.